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Old 29-06-2022, 11:56   #1
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Fibreglass thought? foredeck core replacement

Hi all!
after founding out that a large part of the balsa core in the foredeck is rotten, its time to replace it. To that i need to use some fibreglass to close up the deck again, after the new core has been placed.

so far i have three candidates of fibreglass to use, fyi following numbers are measured in [g/m^2] and i'm gonna use Epoxy for the fibreglass

-900 Biaxial combi with a layer of csm
-Either a 800 or 1200 Triaxial woven mat
-800 Quadriaxial woven mat

which would you go for?

looking forward to hear your thought!
-MV
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Old 29-06-2022, 12:36   #2
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Re: Fibreglass thought? foredeck core replacement

I love baltech so I’d replace balsa with balsa. Quadaxiel is overkill. More for thinner hull sides or building up transom and chines.
800 gets really good saturation 1200 you need to vacuum bag or get real lucky.
I’ve done a patch in port side about a foot behind the bow. The boat sank but no water got in the balsa deck and the hull is solid.
I started my patch with very fine glass on 3 layers. Then heavy weights. I’ve even used .30 and .50 cloth to do minor repairs
The bow has no interior but even the interior looks factory gel coat. The boat skipped along a rock at a pretty good speed. It’s a Donzi 18. The hit tore the lower end of the drive off. Insurance wrote it off and I dove on it to bring it up. Took two inflation bags we nicknamed the Chrysler bag cause one will pick up a 70’ Chrysler wagon.
The bow damage was bad but there were 4 other damaged areas one on the chine I used .50 cloth to fill 1/8” damage.
I’d even suggest using a layer of Matt as a filler on a deck between cloth.
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Old 29-06-2022, 12:45   #3
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Re: Fibreglass thought? foredeck core replacement

Matt flexes less than cloths. Down side is it’s prone to voids
Boat makers that ran a few interior trusses seem to have dodged failing decks.
Some of the most expensive famous brands have a separation problems there and hull chines. Not the chopper gun boats either. Hand laid QC slips. 30 years later delaminating
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Old 29-06-2022, 13:13   #4
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Re: Fibreglass thought? foredeck core replacement

900 biaxial. That will be hard enough to wet out thoroughly with epoxy.
The others will be harder to get wet.
Don't use balsa.
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Old 29-06-2022, 15:31   #5
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Re: Fibreglass thought? foredeck core replacement

Biaxial and Divinycell.
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Old 29-06-2022, 15:33   #6
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Re: Fibreglass thought? foredeck core replacement

I would use the biax and foam also. Not a fan of mat with epoxy work. Just adds extra weight with little added strength
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Old 29-06-2022, 17:12   #7
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Re: Fibreglass thought? foredeck core replacement

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I would use the biax and foam also. Not a fan of mat with epoxy work. Just adds extra weight with little added strength
Epoxy does not bond well with mat as it does not dissolve the binder holding the mat together (polyester does).
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Old 29-06-2022, 17:35   #8
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Re: Fibreglass thought? foredeck core replacement

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Epoxy does not bond well with mat as it does not dissolve the binder holding the mat together (polyester does).
Exactly. That’s the other reason. It simply becomes added weight. It’s not really doing much.
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Old 29-06-2022, 17:42   #9
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Re: Fibreglass thought? foredeck core replacement

I have a few thoughts on balsa core
Balsa Core = Compost on our website.
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Old 29-06-2022, 19:39   #10
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Re: Fibreglass thought? foredeck core replacement

Every boat builder is using end grain balsa on deck and couch roof. I know a few were using foam again. Should be fun. Plywood never connected.
I have an inner and outer mould layer Kevlar roving Vinylester gel coats balsa core.
Replace it like the manufacture. Trust them not us
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Old 29-06-2022, 19:55   #11
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Re: Fibreglass thought? foredeck core replacement

Is there a reason you are not considering attacking this problem from underneath? That would leave the outer deck layer intact, with no need to replicate nonskid areas or re-gelcoat the top surface, or paint it.
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Old 29-06-2022, 20:09   #12
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Re: Fibreglass thought? foredeck core replacement

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Originally Posted by psk125 View Post
Is there a reason you are not considering attacking this problem from underneath? That would leave the outer deck layer intact, with no need to replicate nonskid areas or re-gelcoat the top surface, or paint it.
Good Question.
Maybe tight quarters.
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Old 30-06-2022, 05:42   #13
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Re: Fibreglass thought? foredeck core replacement

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Is there a reason you are not considering attacking this problem from underneath? That would leave the outer deck layer intact, with no need to replicate nonskid areas or re-gelcoat the top surface, or paint it.

That works if there's enough room to do it from underneath, but sometimes interior disassembly plus working against gravity is worse than having to put the cosmetic parts back together.
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Old 30-06-2022, 06:18   #14
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Re: Fibreglass thought? foredeck core replacement

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Epoxy does not bond well with mat as it does not dissolve the binder holding the mat together (polyester does).
I understand you can get CSM with an epoxy soluble binder now? As you say. standard csm should not be used with epoxy for the reason stated.
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Old 30-06-2022, 06:49   #15
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Re: Fibreglass thought? foredeck core replacement

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I understand you can get CSM with an epoxy soluble binder now? As you say. standard csm should not be used with epoxy for the reason stated.
Even if you can, it’s a bad idea. It creates a lesser quality laminate with more weight.

Poor idea in general.
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